Least-K子数组¶

class Solution:
    def countSubarrays(self, nums: List[int], k: int) -> int:
        x = max(nums) # 这里寻找的是最大元素，其实可以换成任何一个指定元素
        right = curr = res = 0
        n = len(nums)
        for num in nums:
            while curr < k and right < n:
                curr += nums[right] == x
                right += 1
            if curr < k:
                break
            elif curr == k:
                res += n - (right - 1) 
                # right指针多走了一步
            curr -= num == x
        return res